This invention relates to an automatic tool changing mechanism for industrial robots to permit programmed replacement of the tool during machining without human intervention and without interruption of the working cycle of the robot. The invention is particularly advantageous in case of bulky or heavy tools and/or tools requiring burdensome connections for power, signals, operating fluids such as water, compressed air, etc., as in the case where the tool is constituted by resistance welding guns or welding yokes although the invention is not limited to such applications.
Hitherto the operation of changing the tool, in particular the welding gun, had to be carried out manually by an operator while the machine was stopped and thus could not be included in an automated working cycle. Thus, the industrial robot, which had been developed to provide maximum versatility of operation due to its great freedom of movement, in practice was paradoxically limited in efficacy by the necessity of having to use one tool for the entire programmed working cycle unlike other numerically controlled machine tools of far less agility such as the so-called machining centers the very attraction of which consists in the possibility of using successively different tools taken from a toolholder magazine during the cycle of working on a workpiece.
It would therefore be desirable to provide the industrial robot with the possibility of changing the tool rapidly and automatically during the programmed cycle in the same manner as is already done in machining centers so that the industrial robot would itself acquire the characteristics of a machining center. The attemps hitherto made for automatically changing the tool on industrial robots have thus proved unsuccessful, particularly in the field of welding.
In fact, in the case of welding robots, on the one hand, one works with particularly heavy and bulky welding guns, which in themselves constitute a heavy strain on the sturdiness of the toolholder head of the robot, and on the other hand, for changing the tool it is necessary to interrupt and subsequently restore numerous service connections for the tool (such as compressed air, cooling water, etc.) including feeding of current of tens of thousands of amperes at low tension to the welding gun.
It is an object of the present invention to provide an automatic tool changing mechanism which permits to change a tool on an industrial robot automatically and rapidly and in timed relation with the working program without rendering the toolholder head of the robot unduly heavy or bulky.
Another object of the present invention is to provide an automatic tool changing mechanism which is capable of effecting in a simple and reliable manner the interruption and restoration of the service connections of the tool, in particular the feeding of electric power, even with heavy currents and low tensions.